Résumé
textlessptextgreaterClimate models predict significant rainfall reduction in Amazonia, reducing water availability for trees. We present how functional traits modulate the tree growth response to climate. We used data from 3 years of bimestrial growth measurements for 204 trees of 53 species in the forest of Paracou, French Guiana. We integrated climate variables from an eddy covariance tower and functional trait values describing life history, leaf, and stem economics. Our results indicated that the measured functional traits are to some extent linked to the response of trees to climate but they are poor predictors of the tree climate-induced growth variation. Tree growth was affected by water availability for most of the species with different species growth strategies in drought conditions. These strategies were linked to some functional traits, especially maximum height and wood density. These results suggest that (i) trees seem adapted to the dry season at Paracou but they show different growth responses to drought, (ii) drought response is linked to growth strategy and is partly explained by functional traits, and (iii) the limited part of the variation of tree growth explained by functional traits may be a strong limiting factor for the prediction of tree growth response to climate.textless/ptextgreater
Auteurs, date et publication :
Auteurs Fabien Wagner , Vivien Rossi , Christopher Baraloto , Damien Bonal , Clément Stahl , Bruno Hérault
Publication : International Journal of Ecology
Date : 2014
Volume : 2014
Pages : 1–10
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Alain Dejean , Jérôme Orivel , Maurice Leponce , Arthur Compin , Jacques H C Delabie , Frédéric Azémar , Bruno Corbara
Publication : Biological Journal of the Linnean Society
Date : 2018
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Yu Bai , Stefano Tebaldini , Dinh Ho Tong Minh , Wen Yang
Publication : IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
Date : 2025
Issue : 99
Pages : 1-7
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouAuteurs, date et publication :
Auteurs Isabelle Maréchaux , Jérôme Chave
Publication : Ecological Monographs
Date : 2023
Volume : 87
Issue : 4
Pages : 632-664
Catégorie(s)
#CNRS #FORET Nouragues #FORET ParacouRésumé
Stoichiometric homeostasis of heterotrophs is a common, but not always well-examined premise in ecological stoichiometry. We experimentally evaluated the relationship between substrate (plant litter) and consumer (microorganisms) stoichiometry for a tropical terrestrial decomposer system. Variation in microbial C : P and N : P ratios tracked that of the soluble litter fraction, but not that of bulk leaf litter material. Microbial N and P were not isometrically related, suggesting higher rates of P than N sequestration in microbial biomass. Shifts in microbial stoichiometry were related to changes in microbial community structure. Our results indicate that P in dissolved form is a major driver of terrestrial microbial stoichiometry, similar to aquatic environments. The demonstrated relative plasticity in microbial C : P and N : P and the critical role of P have important implications for theoretical modelling and contribute to a process-based understanding of stoichiometric relationships and the flow of elements across trophic levels in decomposer systems.
Auteurs, date et publication :
Auteurs Nicolas Fanin , Nathalie Fromin , Bruno Buatois , Stephan Hättenschwiler
Publication : Ecology Letters
Date : 2025
Volume : 16
Issue : 6
Pages : 764-772
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Simple sequence repeat (SSR) markers are widely used tools for inferences about genetic diversity, phylogeography and spatial genetic structure. Their applications assume that variation among alleles is essentially caused by an expansion or contraction of the number of repeats and that, accessorily, mutations in the target sequences follow the stepwise mutation model (SMM). Generally speaking, PCR amplicon sizes are used as direct indicators of the number of SSR repeats composing an allele with the data analysis either ignoring the extent of allele size differences or assuming that there is a direct correlation between differences in amplicon size and evolutionary distance. However, without precisely knowing the kind and distribution of polymorphism within an allele (SSR and the associated flanking region (FR) sequences), it is hard to say what kind of evolutionary message is conveyed by such a synthetic descriptor of polymorphism as DNA amplicon size. In this study, we sequenced several SSR alleles in multiple populations of three divergent tree genera and disentangled the types of polymorphisms contained in each portion of the DNA amplicon containing an SSR. The patterns of diversity provided by amplicon size variation, SSR variation itself, insertions/deletions (indels), and single nucleotide polymorphisms (SNPs) observed in the FRs were compared. Amplicon size variation largely reflected SSR repeat number. The amount of variation was as large in FRs as in the SSR itself. The former contributed significantly to the phylogenetic information and sometimes was the main source of differentiation among individuals and populations contained by FR and SSR regions of SSR markers. The presence of mutations occurring at different rates within a marker's sequence offers the opportunity to analyse evolutionary events occurring on various timescales, but at the same time calls for caution in the interpretation of SSR marker data when the distribution of within-locus polymorphism is not known.
Auteurs, date et publication :
Auteurs Stéphanie Barthe , Felix Gugerli , Noelle A. Barkley , Laurent Maggia , Céline Cardi , Ivan Scotti , Shin-Han Shiu
Publication : Plos One
Date : 2012
Volume : 7
Issue : 7
Pages : e40699
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The analysis of fine-scale spatial genetic structure (FSGS) within populations can provide insights into eco-evolutionary processes. Restricted dispersal and locally occurring genetic drift are the primary causes for FSGS at equilibrium, as described in the isolation by distance (IBD) model. Beyond IBD expectations, spatial, environmental or historical factors can affect FSGS. We examined FSGS in seven African and Neotropical populations of the late-successional rain forest tree Symphonia globulifera L. f. (Clusiaceae) to discriminate the influence of drift-dispersal vs. landscape/ecological features and historical processes on FSGS. We used spatial principal component analysis and Bayesian clustering to assess spatial genetic heterogeneity at SSRs and examined its association with plastid DNA and habitat features. African populations (from Cameroon and São Tomé) displayed a stronger FSGS than Neotropical populations at both marker types (mean Sp = 0.025 vs. Sp = 0.008 at SSRs) and had a stronger spatial genetic heterogeneity. All three African populations occurred in pronounced altitudinal gradients, possibly restricting animal-mediated seed dispersal. Cyto-nuclear disequilibria in Cameroonian populations also suggested a legacy of biogeographic history to explain these genetic patterns. Conversely, Neotropical populations exhibited a weaker FSGS, which may reflect more efficient wide-ranging seed dispersal by Neotropical bats and other dispersers. The population from French Guiana displayed an association of plastid haplotypes with two morphotypes characterized by differential habitat preferences. Our results highlight the importance of the microenvironment for eco-evolutionary processes within persistent tropical tree populations.
Auteurs, date et publication :
Auteurs Paloma Torroba-Balmori , Katharina B. Budde , Katrin Heer , Santiago C. González-Martínez , Sanna Olsson , Caroline Scotti-Saintagne , Maxime Casalis , Bonaventure Sonké , Christopher W. Dick , Myriam Heuertz , Zhengfeng Wang
Publication : Plos One
Date : 2017
Volume : 12
Issue : 8
Pages : e0182515
Catégorie(s)
#CIRAD #FORET ParacouRésumé
ABSTRACTMicrowave radiations below say 1250 MHz penetrate forests, dry ice and rocks. The use of airborne or satellite borne microwave sensors to image the subsurface with significant penetration is thus of high interest to analyse wide areas or even to make global surveys. Due to the large distance from the targets, the antenna has to be synthesized using a progressive scan and illuminating the targets from different positions. The radar returns are then properly combined using a computer. The position of the sensor has to be known to a fraction of a wavelength. This is rather easy to obtain if the sensor flies along a well-characterized track (synthetic aperture radar (Bamler and Hartl, 1998)). The creation of the across track aperture is much more difficult. It can be done by using many flights or orbits, which positions, however, need to be extremely well known. We show that this can be obtained by exploiting the characteristics of the targets. We will present the results obtained with airborne campai...
Auteurs, date et publication :
Auteurs Fabio Rocca , Stefano Tebaldini , Dinh Ho Tong Minh
Publication : Annals of GIS
Date : 2016
Volume : 22
Issue : 2
Pages : 103–112
Catégorie(s)
#CIRAD #FORET ParacouRésumé
We predict stand basal area (BA) from small footprint LiDAR data in 129 one-ha tropical forest plots across four sites in French Guiana and encompassing a great diversity of forest structures resulting from natural (soil and geological substrate) and anthropogenic effects (unlogged and logged forests). We use predictors extracted from the Canopy Height Model to compare models of varying complexity: single or multiple regressions and nested models that predict BA by independent estimates of stem density and quadratic mean diameter. Direct multiple regression was the most accurate, giving a 9.6% Root Mean Squared Error of Prediction (RMSEP). The magnitude of the various errors introduced during the data collection stage is evaluated and their contribution to MSEP is analyzed. It was found that these errors accounted for less than 10% of model MSEP, suggesting that there is considerable scope for model improvement. Although site-specific models showed lower MSEP than global models, stratification by site may not be the optimal solution. The key to future improvement would appear to lie in a stratification that captures variations in relations between LiDAR and forest structure.
Auteurs, date et publication :
Auteurs G. Vincent , D. Sabatier , L. Blanc , J. Chave , E. Weissenbacher , R. Pélissier , E. Fonty , J.-F. Molino , P. Couteron
Publication : Remote Sensing of Environment
Date : 2012
Volume : 125
Pages : 23–33
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Mapping forest aboveground biomass (AGB) has become an important task, particularly for the reporting of carbon stocks and changes. AGB can be mapped using synthetic aperture radar data (SAR) or passive optical data. However, these data are insensitive to high AGB levels (textgreater150Mg/ha, and textgreater300Mg/ha for P-band), which are commonly found in tropical forests. Studies have mapped the rough variations in AGB by combining optical and environmental data at regional and global scales. Nevertheless, these maps cannot represent local variations in AGB in tropical forests. In this paper, we hypothesize that the problem of misrepresenting local variations in AGB and AGB estimation with good precision occurs because of both methodological limits (signal saturation or dilution bias) and a lack of adequate calibration data in this range of AGB values. We test this hypothesis by developing a calibrated regression model to predict variations in high AGB values (mean textgreater300Mg/ha) in French Guiana by a methodological approach for spatial extrapolation with data from the optical geoscience laser altimeter system (GLAS), forest inventories, radar, optics, and environmental variables for spatial inter- and extrapolation. Given their higher point count, GLAS data allow a wider coverage of AGB values. We find that the metrics from GLAS footprints are correlated with field AGB estimations (R2=0.54, RMSE=48.3Mg/ha) with no bias for high values. First, predictive models, including remote-sensing, environmental variables and spatial correlation functions, allow us to obtain “wall-to-wall” AGB maps over French Guiana with an RMSE for the in situ AGB estimates of ∼50Mg/ha and R2=0.66 at a 1-km grid size. We conclude that a calibrated regression model based on GLAS with dependent environmental data can produce good AGB predictions even for high AGB values if the calibration data fit the AGB range. We also demonstrate that small temporal and spatial mismatches between field data and GLAS footprints are not a problem for regional and global calibrated regression models because field data aim to predict large and deep tendencies in AGB variations from environmental gradients and do not aim to represent high but stochastic and temporally limited variations from forest dynamics. Thus, we advocate including a greater variety of data, even if less precise and shifted, to better represent high AGB values in global models and to improve the fitting of these models for high values.
Auteurs, date et publication :
Auteurs Ibrahim Fayad , Nicolas Baghdadi , Stéphane Guitet , Jean-Stéphane Bailly , Bruno Hérault , Valéry Gond , Mahmoud El Hajj , Dinh Ho Tong Minh
Publication : International Journal of Applied Earth Observation and Geoinformation
Date : 2016
Volume : 52
Pages : 502–514